The present invention relates to a device which is particularly but not exclusively useful for compensating the internal and external pressures in double-glazing units.
Conventional double-glazing units are becoming increasingly widespread in the field of constructions, as well as in other fields, said double-glazing units being particularly appreciated because of their thermal and acoustic insulation features.
All currently commercially available double-glazing units have a substantially common structure despite the variety of their embodiments.
In particular, a double-glazing unit is constituted by a frame which supports two sheets of an at least partially transparent material, between which a chamber is provided which is adapted to form an air space for thermal and acoustic insulation.
This air space, usually filled with isolated air, gives double-glazing units their particular characteristics.
In some particularly advanced double-glazing units, means for blocking sun rays, such as for example blinds, roll-up shutters, Venetian blinds, or others can slide inside the chamber formed by the sheets.
In double-glazing units, one of the two sheets is normally exposed to the outside environment whilst the other one is exposed to the inside environment of the building.
This arrangement of double-glazing units causes them to be in contact with temperatures which are sometimes considerably different from each other.
Moreover, as known, the temperature increases inside the double-glazing unit due to the greenhouse effect when it is struck by the sun rays, indeed because some of the rays are captured and reflected several times between the facing inner and outer surfaces of the two sheets.
These behaviors cause a difference in temperature and especially in pressure between the air inside the chamber formed by the two sheets and the outside pressures.
This pressure gradient causes a significant deformation of the sheets which leads to many drawbacks.
Among these drawbacks, the generation of reflections, which are particularly unpleasant and sometimes dangerous for people outside the building, should be mentioned in the case of reflective sheets for outdoor use.
Another drawback, particularly for double-glazing units in which sliding blocking means are inserted, is the reduction in the functionality of said means, which are prevented from sliding smoothly by the sheet deformations.
Sometimes, in cases in which the deformation of the sheets becomes particularly significant, the darkening means are fully prevented from sliding, thus completely losing their functionality.
In order to eliminate this drawback, valve means have been conceived for compensating the internal and external pressures; however, said means have not yielded satisfactory results, since they exhibit a certain delay in their compensating response when the pressure gradient occurs and increases and also because any air drawn from the outside has a certain moisture degree which is particularly harmful inside the double-glazing unit.
In addition to applying valve means, it is therefore necessary to provide, for this purpose, moisture absorbing means such as hygroscopic salts, which however must also be replaced appropriately, since they quickly saturate, especially in very moist environments.
Another compensation method has been obtained by providing deformation-absorbing regions constituted by membranes made of an elastic material.
In this case, too, the compensating response of the membranes is not ideal, since said membranes move when the pressure gradient is already too high and therefore the sheet is already deformed.